PROJECT SUMMARY/ABSTRACT Attention lapses refer to transient periods of off-task performance characterized by processing delays and errors across a range of cognitive tasks and everyday activities. Attention lapsing is a feature of a number of mental health disorders, including depression, ADHD and schizophrenia. Lapsing contributes significantly to cognitive impairments in these disorders. Here we aim to test a theoretical model in which attention lapses are regulated by the suite of cognitive control functions mediated by the prefrontal cortex (PFC). Increased cognitive control demands on a variety of tasks have been tightly linked to coordinated neural activity in the theta frequency band (4-7 Hz) using electrophysiology (EEG). We hypothesize that stimulation of the PFC will enhance control-related theta activity and attentional control, leading to fewer attention lapses and improved cognitive performance. Attention lapses will be measured both behaviorally and by coordinated neural activity in the alpha frequency band (8-12 Hz). We propose to test these hypotheses using a within-participants, double-blind design that will measure behavioral and EEG theta- and alpha-band measures of cognitive control and attention lapses following active PFC-targeted transcranial direct current stimulation (tDCS), compared to Sham and Active Control stimulation (targeting occipital cortex, a region not hypothesized to support attentional control). We further propose to test our model of PFC-mediated attentional control by assessing individual differences in tDCS effects, using structural neuroimaging and computational modeling of current flow. This proposal has two specific aims. Aim 1: Test an expanded model of cognitive control by evaluating the impact of PFC-targeted tDCS on frontal theta oscillations (4-7 Hz) related to cognitive control and alpha oscillations (8-12 Hz) related to attention lapses. Aim 2: Test an expanded model of cognitive control using biologically-realistic modeling to assess individual differences in tDCS effects. The proposed work contains several key theoretical and technical innovations, including the conceptualization of attentional control as a PFC-mediated executive function, the use of an active control condition and the focus on the neural underpinnings of attention lapses. This project will provide unique data towards our understanding of how coordinated neural activity in the theta and alpha bands is related to lapsing and the extent to which the electrophysiological patterns supporting attentional control can be modified using non-invasive neurostimulation targeting the prefrontal cognitive control system. This would be of substantial value both to the neurostimulation research community and, as lapsing is a core feature of psychopathology in many psychiatric disorders, to mental health research more broadly.